This invention relates to electronically operated telephone use control apparatus that can be added to an existing telephone.
Existing add-on telephone timing devices generally use a simple clock device to measure the duration of a telephone call. The clock device is normally off, and is turned on and off when and if the user remembers to do so.
Mechanical switches, such as that described in U.S. Pat. No. 4,473,718, are employed to time calls. These mechanical switches are switched from one state to another when the telephone handset is lifted out of, or replaced in, its cradle.
The prior art add-on timing devices are not part of the telephone, do not take their signals or cues from the telephone line, and depend on mechanical rather than electrical activation. They required batteries to deliver the power required to operate the device. Either expensive and cumbersome battery rechargers were required, along with expensive batteries, or the most expensive batteries were employed. In the latter case, battery life was relative short, and in the former case, a precious separate electrical outlet was taken for use by the timing device. The timing device was also subject to line voltage spikes and to damage in the absence of protective means in the recharging circuit or the device itself, another expensive element.